Propeller clutch



July 26, 1949. G. w. MARTIN PROPELLER CLUTCH Filed NOV. 16, 1945 WMV a, WW

Patented July 26, 1949 UNITED ESTATES PAT ENT OFFICE EPR-OPELLER CLUTCH George W..Marti, Eau claire, wis.

Appli'oationNovemher 16, 1945,1Serial No.162:`9,063

(Cl. V64u29) -4 Claims. `1 This invention :relates to boat propellers, and haszto do-withc1utchrmeans for establishing driving connection*between-'therpropeller Vand its associated shaft.

In propeller :driven boats, including Aboats having `inboard `motors fandlcoats having outboard motors, particularly whensuclr boats areoperated insshallow water for in :water yin `which Vsubmerged objects may :be present, :there is the possibility .thatthe'propellerxmaystrikea submerged object, causingdamage :to `the .propeller or to some :portion ofthe driving mechanism, or to both. In Aorderto reducefthat riskcit isknown to provide a shear pin-at asuitable point inthe .propeller drive, of `such `character:thatfifthepropeller strikes an 1 unyielding object the pin will `shear `before damage `is caused to -the :propeller forithe associated mechanism. `In some cases aresilient cushion member is inserted in ithe Kpropeller `drive 4for the purpose iof iabsorbing shock `when :the propeller strikes an unyielding object, tto thereby further `protect :the kpropeller mechanism. Also, friction drive has been included :in :thepropeller mechanism to `allowfslippage upon occurrence of abnormal resistance'to rotation ofthe propeller. lIn certain `of the `mechanismsreferred to, `rubber is used as "the {cushioning-1 material or: in part of the 'friction driveiand, in: some:cases,ihasaprovedftov be ,highly `eilicient infgeneral The use -of a friction drive :incurs the risk that, `if `the .parts `are not properly-adjusted, nndesiredfslippage:between the friction :membersmayroccur with' resultant lossV in `iiriving--eiciencv andpbjectionable ,Wear'thereot -The `use fofzrubber in propeller clutches of the character referred to isfopen tothe objection that if the rubber isnot :protected :.by :a metal cover :it may, under hadverse conditions, become vulcanized to the propeller hub, thus rendering the clutchinoperable Tor fits-'intended purpose. Even Vwhere nthe :rubber is properly `protectedby a metal covciting, '1t-may, after long use vand under adverse conditions,fdeteriorate to such `an yextent as to render: it difficult tomaintain proper driving connection Abetween-the propeller :shaft and the pro- -peller :under :intended `normal operating Yconclii" vrthe mechanisms above-:referred to; is "compacte of simple `'and inexpensive construction, :readily Aaccessiblefor inspection, replacement, ior repair, fand :provides positive driving lconnection rbetween the 4:propeller fshaftand the `propeller `hub i under normaloperating conditions while-assuringcdeclutchabnormal vresistance l to :rotation ci the :.propeller.

` tween the prcpellerfshaft and `the propeller, re-

:ingrofiithegpropellerifrom thesshaitgresponsive-to 155 sponsive tri-abnormal resistance'to rotation-of tthe propeller. Farther, the clutch parts are ,of :such character that, .vhendisengagedfor the vpurpese stated, they cooperateto produce an audible signal notifying `the r operator that l abnormal; resistance torotationorthe propellerlhas been-*encountered, so that the enginemay' besstoppeduntirthe cause of-such conditionnhas been investigated-and remedied, thus Vreducing likelihood of injury to either the propeller `or its `associated operating mechanism. `AFurther cbj ects and Aadvantages of my invention willappear fromfthe ,detailed-esemption. 4

`Inthe drawings:

'Figure 11 is a sternview"ofiazgearfhousing and propeller unit embodying the clutch 'of my invention, intendedfor use` with` an :outboard motor;

YFigure 2 is a sectional viewzof thepropellenand the asscciatedelutch means, takenisubstantially online 2-2- of :Figure-1,- on arrfenlarged sca1e,with certain :parts shown in `.elevation fand :the fgear housing shown in side view;

`liligure 3 is af sectional `iview `ftalnen substantially on line 3--3 of Eigure2;

Figure v,.4 is 4anzouter giace view #of the :inner clutch; member; and

Figures-is aside-:view-of thetinner clutchxmember.

I=have shown-the-:propeller clutch meansrof :my inventiomby-way (if-example, as .appliedz to azunit intended `for-use withvan outhoardfmotcr. This unit `comprises 1a :gear :housing :6, of suitable construction, `carried atfthe :lower :end fof e a steering tube or Acoluinn'rhaving artrite-:upper .end-` a suitable motor, as `is known. The Tmotor fdrives .fa Shaft 1 extendingrdownwardiinto casing or housing :Gand having driving connect-ion, through gearing therein to va :propeller` shaft :B frotatably `mounted within vhousing :f8 -and y,extending :outward therebeyond. lMy propeller clutchlmeansphereinafter described, is shown mounted on :the propeller shaft-Brinside thepropellerhubl rIt canbeused withany propeller withoutgregard'.toiwhetherthe edriving imotpr :is :of :inboard for routboard itype.

Housing B is provided with the usual downwardly extending skeg 9.

A propeller I0, comprising a hub II and suitably formed and disposed blades I2 secured to the hub, conveniently formed integrally therewith, is mounted on the after portion of propeller shaft 8. The propeller I is restrained against movement lengthwise of shaft 8 aft by a cap nut I3 screwing on the after end of shaft 8 in contact with a washer I4 abutting the after end of hub II, nut I3 being normally restrained against turning movement on shaft 8 by a ycotter pin I5 passing through a diametrical slot I6 in shaft 8 and through diametrically opposite bores i3d in nut I 3. Any other suitable means may be provided7 within the field of my invention, for restraining nut I3 against turning movement relative to shaft 8.

The hub II of propeller IU is of hollow construction for the major portion of its length, open at its forward end, and is provided at its thickened outer or after end portion I Ia with an axial bore of a diameter to receive shaft-8 snugly but not tightly.

Propeller hub II is provided interiorly thereof with a plurality, for example four, of forwardly opening grooves I8 arranged radially and extending lengthwise thereof. The grooves I3 receive corresponding bosses or tongues I9 formed integrally with and projecting radially outward from an after disc-shaped clutch member 2li loose on shaft 8 and disposed within the body of hub I I. The member 20 is provided at its forward end or face with a plurality of radially disposed clutch elevents in the form of teeth 2|'. The teeth 2l normally interengage with similar teeth or clutch elements 22 at the after end or face of a forward clutch member23 disposed about shaft B. The clutch member 23 is provided, in its forward face, with aligned radially extending grooves 24 which receive the end portions of a shear pin 25 extending through shaft 8 diametrically thereof. A coil compression spring 2'I is disposed about propeller shaft 8 and is confined between the after end wall I Ia of hub II and the after clutch member 20, normally effective for holding this member in clutching engagement with the forward clutch member 23, the latter being restrained against forward movement lengthwise of shaft 3 by shear pin 25 which, as noted, engages in grooves 2li of member 23 and establishes positive driving connection between this member and shaft 8. K

From what has been said, it will be seen that so lo/ng as the members 20 and 23 are held in clutching engagement, the propeller hub II has positive driving connection to the propeller shaft i! so that no slippage between parts occurs and the propeller is driven at the same speed as the propeller shaft. Referring particularly to Figure 5, the teeth 22 of the forward clutch member 23 taper forward axially thereof. The amount or rate of taper of teeth 22 may vary considerably, though I have found that for use with ordinary two-cylinder outboard motors a taper such that the side surfaces of teeth 22, at the circumference of member 23, are inclined at an angle of approximately 30 to the horizontal is highly efficient and suitable for most conditions encountered in practice. As will be readily understood, the teeth 2l of the after clutch member 20 are complementary to teeth 22 of the forward clutch member 23 and are tapered similarly but oppositely to the latter teeth; The nut I3 provides means whereby the propeller may readily be adjusted on shaft 8 in proper relation to the gear housing 6, the necessary movement of the propeller lengthwise of shaft 8 for that purpose being rather slight. The rate or strength of spring 2l is such that the adjustment of the propeller has practically no effect with respect to the force exerted by this spring for holding clutch member 20 in clutching engagement wtih clutch member 23. Under normal conditions the propeller is clutched to and positively driven by the propeller shaft 8, but if abnormal resistance is offered to rotation of the propeller, as when the propeller strikes an obstacle which produces an objectionable overload, the propeller will be automatically declutched from the shaft 8, as will be explained more fully presently.

The teeth of the clutch members 2i! and 23 are oppositely tapered, as noted, and when objectionably high resistance is offered to rotation of the propeller the contacting side surfaces of the teeth of the clutch members create a component of force which tends to force these members apart. It will be apparent that the angle of inclination of the teeth of the clutch members, and the force exerted by spring 21 on the clutch member 20, which force is substantially constant, as noted, determine the load at which the clutch members 20 and 23 will become disengaged so as to declutch the propeller from the shaft 8. The teeth of the clutch members 223 and 23 thus constitute clutch elements normally engaged and establishing positive driving connection between the members 2!) and 23, such elements being disposed and adapted to cause declutching of the members 20 and 23 so as to declutch the propeller from shaft 8, responsive to the propeller encountering objectionably high resistance to its rotation. When the propeller encounters such abnormal or objectionably high resistance to its rotation-for example, when a propeller blade strikes a submerged object-the clutch member 2B is displaced aft from clutch member 23, as permitted by the elongated grooves I3 in hub Il and in opposition to spring 21, thus declutching the propeller hub from shaft 8. When that occurs, the clutch member 23 continues to rotate with shaft 8, and the teeth thereof striking or clashing the teeth of member 20 produce an audible signal serving to warn the operator or occupant of the boat that the propeller has encountered an obstruction preventing its rotation. When that occurs, the operator can quickly stop the engine and then investigate, removing the obstruction or moving the boat into position in which the propeller clears the obstruction, the members 20 and 23 bei-ng then automatically clutched together, after which the boat may proceed on its way.

It will be clear from the above that the propeller clutch of my invention does not necessitate the use of rubber or like material which, under adverse conditions, may tend to become vulcanized to associated metal parts. All of the parts of the clutch of my invention are formed of suitable metal and may readily be formed by die casting, which is advantageous as avoiding necessity of machining and is conducive to low cost of production. The amount of overload at which the clutch operates,` being determined by the angle of the teeth and the strength of the spring, is not adjustable. Consequently, it cannot be improperly adjusted by a user. The angle and the spring strength can be properly combined by the manufacturer to insure protection of the motor. The shear pin is added insurance againstV damage to the driving parts. The clutch means is, as a whole, of comparatively simple construction and may readily be disassembled for replacement or repair of parts, and as readily reassembled, which is of practical importance in devices of this character.

It will be understood that changes in construction and arrangement of parts of `the clutch means of my invention may be resorted to without departing from the fleld and scope thereof, and I intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred form only of my invention has been disclosed.

I claim:

1. In propeller clutch means of the character described, a propeller shaft and a propeller thereon restrained against movement in one direction lengthwise of said shaft, two cooperating clutch members loose on said shaft, one having tongue and groove driving connection to said propeller and the other having positive driving connection to said shaft and being restrained against movement lengthwise thereof in a direction away from said one member, the latter being movable relative to said propeller lengthwise of said shaft in a direction away from said other member, and yielding means normally holding said one member in engagement with said other member, said clutch members having interengaging clutch elements normally establishing positive driving connection therebetween disposed and adapted to cause movement of said one member away from said other member into position disconnecting the driving connection therebetween responsive to abnormal resistance to rotation of said propeller, the latter being otherwise free from said shaft with respect to rotation thereof.

2. In propeller clutch means of the character described, a propeller shaft and a propeller thereon comprising a hub restrained against aftward movement lengthwise of said shaft, an aftward clutch member loose on said shaft having tongue and groove connection to said hub, a forward clutch member loose on said shaft having positive driving connection thereto and restrained against inward movement lengthwise thereof, and yielding means urging said hub aftward and said after clutch member forward along said shaft, said clutch members having interengaging clutch elements normally establishing positive driving connection therebetween disposed and adapted to cause aftward movement of said after member into position disconnecting the driving connection between said clutch members responsive to abnormal resistance to rotation of said propeller, said propeller hub being otherwise free from said shaft.

3. In propeller clutch means of the character described, a propeller shaft and a propeller thereon comprising a hub restrained against aftward movement lengthwise of said shaft, an after clutch member loose on said shaft having tongue and groove connection to said hub provided with forwardly directed clutch teeth, a forward clutch member loose on said shaft having positive driving connection thereto and restrained against forward movement lengthwise thereof, said forward member having aftwardly directed clutch teeth disposed and adapted for interengagement with the teeth of said after member effective for establishing positive driving connection therebetween, and yielding means urging said after clutch member forward effective for maintaining it normally engaged lwith said forward clutch member, the teeth of said clutch members being tapered aX- ially thereof in opposite relation effective to cause aftward movement of said after member into position disconnecting the driving connection between said clutch members responsive to abnormal resistance to rotation of said propeller, said propeller hub being otherwise free from said shaft.

4. In propeller clutch means of the character described, a propeller shaft and a propeller thereon comprising a hub restrained against aftward movement lengthwise of said shaft, an after clutch member loose on said shaft having tongue and groove connection to said hub provided at its forward face with radially disposed inwardly directed clutch teeth, a forward clutch member loose on said shaft having positive driving connection thereto restrained against forward movement lengthwise thereof, said forward member having at its after face radially disposed aftwardly directed clutch teeth adapted for interengagement 4with the clutch teeth Iof said after member effective for establishing positive driving connection therebetween, and yielding means urging said after clutch member forward effective for maintaining it normally engaged with said forward clutch member, the teeth of said clutch members being tapered axially thereof in opposite relation effective to cause aftward movement of said after member into position disconnecting the driving connection between said clutch members responsive to abnormal resistance to rotation of said propeller, said propeller hub being otherwise free from said shaft.

GEORGE W. MARTIN.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,860,750 Riggs May 31, 1932 1,864,716 Doremus June 28, 1932 1,999,523 Willoughby Apr. 30, 1935 2,164,485 Yantis July 4, 1939 

